Managing caustic exposures in primary care

Caustic injuries: An uncommon but significant cause of morbidity

Caustic injury occurs when a substance causes direct tissue damage upon contact.¹ It typically involves denaturation of biological proteins by one of six chemical reactions: oxidation, reduction, corrosion, desiccation, vesication or protoplasmic poisoning.² The terms “corrosive” and “caustic” are often used interchangeably, however, corrosion is a specific process of mechanical degradation; all corrosives are caustic, but not all caustics are corrosive.³ Acids and alkalis are commonly associated with caustic injuries, but other substances can also cause caustic injury, including desiccants (e.g. calcium oxide/chloride in moisture absorbers), vesicants (e.g. mustard gas), surfactants (e.g. surface wetting agents) and alkali group metals (e.g. sodium, potassium).³

Mechanisms differ but management is the same

Acids and alkalis are the most likely caustic substances that people will be exposed to (see: “Caustic chemicals are readily available”). Any exposure to a chemical with a pH of < 3 or > 11 has the potential to cause significant injury, e.g. perforation of the oesophagus.¹ The mechanism of injury for acids and alkalis differs slightly, but in most cases this does not affect the decontamination or management of a patient with a caustic exposure (an exception is hydrofluoric acid – see: “Focus: Hydrofluoric acid exposures”).¹

Read more

Routes of exposure to caustic substances

Severe chemical burns over large body surface areas have the potential to cause systemic effects, e.g. dehydration, metabolic and electrolyte disturbances, hypothermia (due to persistent irrigation of the affected area).⁶

For tools to aid estimation of the total body surface area affected by a burn, see: www.nationalburnservice.co.nz/policies-and-guidelines/

Exposure characteristics influence outcomes

Caustic ingestions most commonly occur in young children (aged five years and under) and involve household cleaning products.⁵ These ingestions are generally exploratory in nature, seldom involve large quantities and are less likely to result in severe injury.^{3, 12} Accidental caustic ingestions by adults or older children are less common, but may occur if caustic agents are stored in drinking vessels or other unlabelled containers.

N.B. Dishwasher detergents (e.g. powder) were previously a common cause of paediatric caustic injuries in New Zealand. Legislation was passed in 2006 prohibiting the sale of dishwashing products with a pH of > 12.5 with the aim of reducing the risk of injury if ingested.^{13, 14}

Workplace exposures often present an increased injury risk due to the higher concentrations of industrial chemicals.⁴ Based on available evidence, most patients requiring admission to burn centres in Australia and New Zealand for dermal caustic injuries are males who are injured in the workplace.¹⁵ Males are also more likely to experience ocular caustic injuries, however, these more commonly occur at home, where the use of eye protection is less likely than in workplaces (where it is a health and safety requirement).¹⁶

Intentional exposures in adolescents and adults are the most concerning caustic injuries; large quantities are typically consumed with the intention of self-harm, resulting in significant injury and potentially, death.³

Assessing a caustic exposure in primary care

The potential severity of a caustic injury is determined by the volume of chemical the person is exposed to, the concentration, its physical state and its pH.¹ The titratable reserve of the substance (i.e. the quantity of acid or alkali required to neutralise the substance) is also an indicator of likely injury severity, however, it is unlikely this information will be known and it does not affect management in primary care.¹

Initial evaluation

Most people (or parents/caregivers of children) who ingest or are exposed to a caustic substance will contact the National Poisons Centre, or present to an urgent care clinic or emergency department. There will be occasions, however, when a general practice is the first point of contact.

Caustic exposure risk assessment

After confirming that the patient is stable, perform a comprehensive risk assessment, followed by a physical examination to evaluate their clinical condition and guide management (Figure 1).

Clinical features do not always correlate with injury severity for caustic ingestions

As a precaution, all patients who have ingested (or are likely to have ingested) a caustic substance require a period of medical observation to ensure symptoms do not develop or worsen, e.g. gastrointestinal pain, vomiting, difficulty swallowing, airway oedema (see: “Endoscopy is the gold standard for assessing caustic ingestion”).

The presence of severe oesophageal or gastric injury cannot be excluded based on an absence of symptoms alone;⁵ a retrospective study of 206 children who underwent endoscopy following caustic ingestion found that 19% who were asymptomatic had evidence of oesophageal injury.¹⁷ Conversely, evidence of mouth or oropharyngeal injury does not necessarily mean that caustic injury has occurred further along the upper gastrointestinal tract, especially in the case of children who ingest small quantities.³

Caustic exposure management

Management following a caustic exposure focuses on first aid and supportive care. Resources often limit the interventions that can be provided in primary care, therefore in most cases, immediate referral to the emergency department (by ambulance if required) is more practical. Some patients who are asymptomatic or only mildly symptomatic following a caustic exposure may still require assessment and observation in the emergency department, due to the potential for clinical deterioration.

In situations where primary care clinicians need to provide emergency management to a patient before referral, or timely referral to hospital is not practical or possible, e.g. rural location, an understanding of caustic exposure management “basics” is useful.

Best Practice Tip: Contact the National Poisons Centre for chemical-specific monitoring and management advice. Phone 0800 764 766.

Ingestion or oral exposure

An obstructed airway is the main clinical concern following a significant caustic ingestion.^{3, 18} This can result from the initial swallowing of the chemical, involuntary vomiting or oesophageal oedema.³ Systemic symptoms are possible with large or highly concentrated caustic ingestions, e.g. metabolic acidosis, disseminated intravascular coagulation, multi-system organ failure, sepsis, shock.^{4, 18}

Generally, all patients who swallow concentrated caustic substances require emergency department referral, regardless of symptoms.³ Even small volumes of concentrated caustic substances can cause significant oral injury and oedema, potentially leading to delayed airway compromise. Patients usually need to be observed for 4 – 24 hours, which is not practical for most primary care clinics. However, there may be some circumstances where medical observation in primary care is necessary, e.g. an asymptomatic patient in a rural location. Asymptomatic adult patients should be monitored for at least four hours, and longer observation periods may be necessary for children.⁴ Withhold food and fluids during this time. The patient can be sent home after this period if they remain asymptomatic and can tolerate eating and drinking, but should continue to be monitored by an appropriate adult.⁴ Review or check in with the patient after 24 hours to confirm they have not developed symptoms suggestive of an upper gastrointestinal injury, e.g. pain, vomiting, difficulty swallowing.

In situations where a patient has accidently taken a mouthful of a concentrated caustic substance but spat it out, the mouth should be rinsed and the patient observed in a healthcare setting for four hours. If the patient is being observed in primary care, the development of swelling or increasing pain should prompt referral to hospital. If the patient is asymptomatic after this period, they can be sent home with instructions to re-introduce fluids followed by small amounts of food, as tolerated, but should continue to be monitored by an appropriate adult. Note that in some cases, patients may not realise they have ingested the substance, due to natural swallowing reflexes.

For asymptomatic patients who have ingested a very small quantity of a diluted caustic product, observation at home with an appropriate adult for four hours is reasonable. Food and fluids should be withheld. After four hours, gradual re-introduction of fluids, then small amounts of foods, can occur. Medical attention should be sought if the patient develops symptoms, e.g. oral or pharyngeal pain, difficulty swallowing.

Caustic dermal exposure management

Immediate irrigation of affected skin with copious amounts of running water is advised for almost all^* caustic dermal exposures, e.g. under a tap, in the shower, with a hose.^{6, 8} Early and effective decontamination can reduce injury severity.^{6, 7} Contaminated clothing should be removed, along with any jewellery.^{7, 19} Following irrigation, consider debriding blisters over joints as these may put pressure on the injured area.¹⁹

* Do not irrigate injuries caused by alkali group metals (e.g. sodium) with water as this may cause an exothermic reaction and further tissue damage. Cover any visible metal with mineral oil or surgically remove, if possible.

All patients with more than mild, resolving skin irritation following a caustic dermal exposure require emergency department referral after initial first aid, for assessment and monitoring.⁸ Arrange an ambulance in more severe situations, as this may allow continued irrigation of the injury while traveling to hospital.

Caustic injuries should be managed as full-thickness burns until the clinician is confident of injury severity, however, evaluation of injury depth is challenging.⁶ First-degree chemical burns can be managed in the same way as thermal burns, i.e. clean, simple analgesia, non- or low-adherent dressing. Further management may not be required if the patient is asymptomatic following irrigation and there is no evidence of chemical injury apart from mild erythema. Advise patients to monitor the area over the next two to three days as burn injuries can progress over time and seek medical attention if the site of exposure becomes symptomatic, e.g. pain, blistering. The exception to this is hydrofluoric acid burns, which may be painless initially, but all exposures require medical assessment in hospital (see: “Focus: Hydrofluoric acid exposures”).

Caustic ocular exposure management

Immediately irrigate eyes with water or normal saline (0.9% sodium chloride) for at least 30 minutes.⁹ Application of topical anaesthetic drops may facilitate more effective irrigation but should not delay it (flushing could be paused momentarily to apply drops).^{20, 21} Ideally, assess ocular pH after 30 minutes of irrigation by applying an indicator strip or litmus paper to the conjunctival fornix.²⁰ Decontamination should continue until the ocular pH has returned to normal, i.e. pH of 7.0 – 7.4 or comparable to the unaffected eye.^{20, 22}

After irrigation, assess:^{21, 22}

• Visual acuity – some reduction in acuity is expected following prolonged irrigation
• Eyelid and eyelash margins, including everting the eyelid – to ensure no chemical is retained
• The cornea and conjunctival surface using fluorescein stain – erythema is common with mild to moderate injury, however, a white appearance of the blanched blood vessels in the conjunctiva and sclera, or corneal haze, suggests more severe injury
• The limbus – limbal ischaemia (pale or blanched appearance) is a poor prognostic indicator, as epithelial stem cells crucial for corneal regeneration may be damaged

All patients who experience a caustic ocular exposure require urgent referral to the emergency department for ophthalmological evaluation for further assessment of the injury, e.g. using slit lamp microscopy, and initiation of treatment(s) to reduce inflammation, manage symptoms and promote healing, e.g. topical steroids, intraocular pressure-lowering agents, ascorbic acid.^{20, 21} Consultation with, or referral to, a specialist ophthalmologist is usually required, but should not delay initial stabilisation which can be carried out/continued in the emergency department.

Best Practice Tip: Consider stocking an “emergency eye kit” to facilitate rapid and effective irrigation following a caustic eye exposure. The kit could include normal saline (in bags and ampoules), topical anaesthetic eye drops, syringes and giving sets, fluorescein strips, pH test strips, Morgan’s lenses (or nasal prongs), cotton buds, gauze and towels.²²

Caustic inhalation management

Management of patients after inhalation of a caustic substance is similar to other acute inhalation injuries, e.g. smoke inhalation.

Symptomatic patients require emergency department referral for hospital observation for up to 24 hours, as upper respiratory swelling may progressively worsen over this period.^{23, 24} Manage bronchospasm using bronchodilators while awaiting transfer to hospital (via ambulance) and administer oxygen where available, and clinically appropriate.^24–26 Endotracheal intubation and mechanical ventilation may be required if the patient’s airway becomes compromised.²⁴

Patients who are asymptomatic or experience mild, resolving symptoms following a brief inhalation exposure can be observed at home over the next 24 hours, ideally with an appropriate adult. Advise them to seek medical attention if they develop any symptoms, e.g. nasal and pharyngeal irritation, coughing, or their existing symptoms worsen over this period.

Follow-up and prognosis for patients who experience caustic injury

Provide home safety counselling

Following a caustic injury, all patients (or parents/caregivers of children) should be counselled about home safety measures to reduce the risk of future exposures, such as:

• Storing chemicals and cleaning products at adult shoulder height or above
• Keeping products in their original containers so they can easily be identified
• Avoiding filling drinking containers, e.g. drink bottles, cups, with substances that are not intended for human consumption